Chilli Dimmers 2410

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HI. We've just had the second batch of chilli dimmers installed at our local theatre and find that the individual dimmer trips operate on cold load when the dimmers are used on a paired circuit. This happens with loads of 2 x parcans (2 x 1kW=8.3A approx) and also 2 x cantatas (2 x 1.2kW=10A approx). Should this happen? Have already set down the topset on the dimmers to 90% but still seem to have problems when dimmers are operated instantaneously from 0-100%. Although during the running of a show this is not a major problem as most scenes are on fades but during setup when the dimmers are operated via remote focussing control the contstant trek to the dimmer racks is becoming tedious. Have we been specified the wrong dimmers or is there something else we can do to eliminate this problem.

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The in rush current on a cold lamp may be somewhere in the region of 13 times the actual rating of the lamp.

I would recommend that you set a preheat level on the dimmer as this will warm the lamps filament, this should be help prevent unwanted tripping.

It is also worth checking that the connections for the load terminal in the dimmer, socket on the bar and plug on the lamp are also nice and tight and no signs of tarnishing etc. If these are not you may be generating a resistance which can generate an arc that which will again cause a current surge.

The other thing to also take into account is your mains supply.

I assume that your calculations are based on a 240v supply, if the supply is lower the current would increase.

This is probably more for the two cantatas as even a drop to 230v would give you a current draw of about 10.4amp.

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Thanks for the info Keith, Preheat may be an option, but the problem is more prevalent when setting up, using the remote focus unit you tend to turn a lantern on full, focus it, move onto the next one. If the dimmers are set to preheat every time they are switched on (i.e. any time anybody is working on the lighting rig / desk) then you could be looking at 20 hours a week in power consumption at 5% is like having the whole rig on for an hour at a time. Having chatted to a few people, they were wondering whether the type of MCCB chosen was causing the problem. I'm no electrical expert but they were talking about type B, C and D fault curves. Any further advice would be appreciated, because I would hate to find out we were specified the wrong type (or max load capacity) of dimmers for our theatre

20m of soca does put in a reasonable bit of resistance to help hold down cold start surges

(even on 2.5mm which is what we are using.)

Local distro is on 30 metres of 16mm SWA from main incomer, so again a reasonable cable length to help hold down the surges.

(at the risk of answering my own question)

I suspect we suffer from having a large local transformer adljacent to the building giving a very low source impedence to our supply.

(3 x 2000 amp incomer to plant room)

Now we could turn up the preheat to glow the pars but I dont really want to do this to the extent filiments are visibly glowing.

Short of swapping to "d" type breakers (need to check if line is low enough loop impedance to do this within regs) anyone got any suggestions.

We have dropped to 2 x 1/2 Kw lamps on some of the worst channels for this problem.

Swapping betapacks for fuse protected dimmers we have no problems so reasonably sure its the mcb surge sensistivity that is the problem.

While using preheat does cut down on the tripping we have found that we get a fairly high filament noise on our preheat , once 100 pars are all on 5% preheat there is a very obvious noise from the grid due to this.

While acceptable for rock n roll where the PA is running high it is not ok for other types of show.

Also 5% preheat on a very large number of channels does draw a reasonable amount of power from the supply.

Our dimmers are on 24hrs a day with no easy central isolation for them. (distributed dimming in our building).